The invention relates to an apparatus and method for use in drilling oil and gas production wells or water injection wells, and more particularly, provides technology which allows two separate and independent wellbores to be drilled through the same wellbore.
Generally, oil and gas production wells and water injection wells are drilled through a large diameter surface structural pipe. As the wellbore gets deeper, changes in water salinity, rock strength and pore fluid characteristics may require additional smaller support casing strings to be installed inside the structural pipe. These additional smaller support casing strings are known as the conductor casing, surface casing and intermediate casing strings. Smaller and smaller casing strings are installed at increasing depth until the rock formation of interest is penetrated and cased with the final production casing. The casing strings are supported by cement. The production casing supplies a conduit for the production tubing through which well fluid flows and maintains the well integrity by keeping the well fluids from escaping. Meanwhile, the inner support casing strings are necessary to the drilling of the well but serve no function after drilling is completed.
As a result of the increased cost of drilling wells into deeper subterranean formations, wellbores are being drilled into formations and orientations by both horizontal and deviated drilling technology. Although horizontal and deviated wells are more expensive than the conventional vertical well, the increased production of hydrocarbons from the subterranean formation can offset the increased costs. Horizontal and deviated wells are especially common on offshore drilling platforms, where the increased production of hydrocarbons from the subterranean formation can be accomplished with fewer platforms by the use of either a horizontal and/or deviated well.
The offshore drilling platforms which are utilized in deep water to drill and complete wells vary in size, structure, and cost depending upon the water depth and the loads in which the platform will be set. In order to reduce the cost of hydrocarbon recovery, multiple wellbores are being drilled through a single surface location involving extra large surface structural pipes through which two casing strings can be run side by side. Although, substantial savings are achieved by drilling two wellbores from a single surface casing, the surface structural pipe in which the two casing strings are run side by side has to be extremely large.
It would be highly desirable to drill two separate and independent wellbores through the same conductor, surface or intermediate casing, thereby saving the duplicate expense of installing the above casing. One way to achieve two separate and independent wellbores is by installation of a drilling assembly which guides the drill bit into one of two different directions, such that two separate wellbores can be drilled into different formations or hydrocarbon zones.
Whipstocks have been used in drilling duplicate wellbores and in order to deviate the wellbore from an essentially vertical course to a desired inclination. A whipstock typically includes tapered sections of round, solid bars which are placed in the wellbore at the desired depth and aligned in the desired direction. The whipstock is typically anchored by a slip mechanism, and used to guide the wellbore tools in a selected direction. The drill bit is guided by the whipstock and mills a window through the casing at the desired location. A second wellbore is then drilled through the casing to the desired formation. When only one deviated borehole is drilled, the whipstock is left in the wellbore to act as a guide for working the well. However, when two or more deviated wellbores are to be drilled from a single wellbore, it is necessary to remove the whipstock. After removal of the whipstock, a re-entry into any of the deviated bore holes is difficult and costly since the whipstock must be placed in the exact location for re-entry.
Another technique for drilling multiple wells through a single casing as disclosed in Gano, et al., U.S. Pat. No. 6,135,208, is through the utilization of a pipe which collapses within its diameter. An expandable wellbore connector is utilized in interconnecting multiple wellbores in the well. The wellbore connector is expanded into a cavity formed in one wellbore, and then another wellbore is drilled through the wellbore connector. The wellbore connector is sealingly engaged with the tubular members in each wellbore.
U.S. Pat. Nos. 5,330,007; 5,458,199; 5,655,602; and 5,685,373 issued to Collins, et al., are all related to a template, and a process utilizing the template, for drilling and completing multilateral wells. The template comprises a body having a first end face, a second end face and a plurality of axially extending divergent bores which extend through the body in intersection with the end faces. The template is secured to a first casing, which extends from the surface to a predetermined depth beneath the surface, or is located at or near the ground surface. A first subterranean borehole is drilled through one of the bores in the template and a first length of production casing is secured to the template such that it extends into the first borehole. Similarly, further subterranean boreholes may be drilled through the further bores in the template and further lengths of production casing may be secured to the template such that the casing extends into its respective borehole.
The Collins, et al. patents describe a conventional tubular riser used to select one of the boreholes. The tubular riser is lowered within the surface casing until the riser is positioned within the first borehole. After drilling the first borehole, the riser is then withdrawn from the bore, rotated, and inserted into a second bore hole. Alternatively, the Collins et al. patents disclose a riser with an orientation cam. The riser and orientation cam is lowered within the casing until a cam key contacts a first slot in the external surface of the cam to orient the rise with the first borehole for drilling the first bore. The riser is then raised from the surface and rotated which causes the riser and cam key to rotate until the key is positioned within a second slot and orientation of the riser in a second borehole is obtained. The second bore is then drilled.
All of these techniques are time consuming, complex and require numerous preparation steps such as under-reaming the wellbore, milling windows in the casing, requiring stats-in inner string cementing equipment or reforming a tube downhole.
Accordingly, it would be desirable to provide an apparatus and method for drilling two separate and independent wellbores through a single surface casing wherein the drill bit can be guided into one of two different directions through the use of a removable guide, and changing wellbores only requires latching the removable guide and rotating the removable guide, which can be performed in a one step operation.
The present invention provides an efficient solution to drilling two separate and independent bore holes through the same surface or conductor casing. The system includes a drilling assembly, a removable guide, and a latching tool.
In accordance with one aspect of the present invention, an apparatus for use in drilling oil and gas production wells or water injection wells includes a drilling assembly having a first end, a second end, and an adapter located in the drilling assembly between the first end and the second end; at least two tubes extending from the adapter, the tubes forming a first leg for drilling a first bore hole and a second leg for drilling a second bore hole; and a removable guide having a first end and a second end, the first end having an angled surface positioned within the guide to direct a drill bit into one of the legs, and the second end configured to engage the adapter in two positions for directing the drill bit into one of the legs.
In accordance with another aspect of the present invention, a removable guide for use with a drilling assembly includes a tubular body having a first end and a second end, the first end having an angled interior surface positioned within the guide to direct a drill bit into one leg of a drilling assembly, and the second end having members configured to engage an adapter in two positions for directing a drill bit into one of two legs of the drilling assembly.
In accordance with another aspect of the present invention, a system for use in drilling oil and gas production wells or water injection wells includes a drilling assembly having a first end, a second end, and an adapter located in the drilling assembly between the first end and the second end; at least two tubes extending from the adapter, the tubes forming a first leg for drilling a first bore hole and a second leg for drilling a second bore hole; a removable guide having a first end and a second end, the first end having an angled surface positioned within the guide to direct a drill bit into one of the legs, and the second end configured to engage the adapter in two positions for directing the drill bit into one of the legs, and a cylindrical body which surrounds the removable guide, the cylindrical body having an outside diameter and an inside diameter wherein the inside diameter has a slot; and a latching tool having a first end and a second end, the first end having a series of threads to attach to a drilling string, and the second end configured to removably engage the slot in the cylindrical body of the removable guide.
In accordance with a further aspect of the present invention, a method of using a drilling assembly includes the steps of drilling a hole to a desired depth; positioning a removable guide in the drilling assembly for directing a drill bit into a first leg of the drilling assembly; securing the drilling assembly to a casing string; cementing the drilling assembly into the surface hole; and drilling a first wellbore through the first leg of the drilling assembly to a desired depth.
In accordance with another aspect of the present invention, a method of using a drilling assembly includes the steps of drilling a hole to a desired depth; securing the drilling assembly having a first and a second leg to a casing string; cementing the drilling assembly into the hole; drilling a first wellbore through the first leg of the drilling assembly to a desired depth drilling; and drilling a second wellbore through the second leg of the drilling assembly to a second desired depth without the use of a movable guide to direct a drill bit into the second leg of the drilling assembly.
The present invention provides advantages of drilling two separate and independent wellbores through the same conductor, surface or intermediate casing, thereby saving expense, and changing wellbores only requires latching the removable guide and rotating the removable guide, which can be performed in a one step operation.